Peptides have been shown to have beneficial cosmetic and therapeutic effects on the skin. In experimental models, short peptides (of length up to 30 amino acids) have been shown to stimulate collagen growth in the extra-cellular matrix of the skin, which may improve the appearance of skin as well as improve the healing of damaged skin (Katayama, et al., 1993, J. Biol. Chem., 268:9941; incorporated herein by reference). Modified peptides have also been shown to decrease the appearance of wrinkles through the modulation of enzymes that influence muscular contractions in the muscles underlying the skin that contribute to wrinkle formation (Lupo, 2005, Dermatol. Surg., 31:832; incorporated herein by reference).
However, a major problem in achieving the potential cosmetic and therapeutic effects of these peptides in humans has been the transdermal delivery of the peptides across the outer skin barrier (stratum corneum) to the site of biological action, e.g., the extra-cellular matrix or underlying muscle (Robinson, et al., 2005, International J. Cosmetic Science 27:155; incorporated herein by reference). To achieve the delivery of transdermal delivery of the peptides in humans, the peptides have had to be chemically modified by the addition of chemical moieties such as but not limited to acetyl and/or palmitoyl groups (Robinson, et al., supra). These chemical modifications are disadvantageous because they are expensive and time-consuming, which negatively impact the commercial manufacture of a product containing these peptides. Chemical modifications of the peptides can also decrease the biological activity of the peptide by decreasing its ability to bind at the cellular receptor site of biological activity (through, for example, steric interference), thus making it less effective. A peptide that is less effective biologically would be less effective for cosmetic or therapeutic purposes. Comparably, a peptide that is less effective biologically would need to be administered at higher levels to achieve its desired biological effect (if the effect were even possible), which would be a cost disadvantage for the commercial manufacture of a product.